The field of the invention is the after treatment of the sulfonation products of non-aromatic hydrocarbon mixtures and the state of the art may be ascertained by reference to U.S. Pat. Nos. 4,177,208 and 4,178,307; French Pat. No. 1,478,530 and West German Patent Application No. F 3718.120, 32/01 of Roderich Graf, Hans Gruschke and Kurt Schimmelschmidt, published Jan. 29, 1953, the disclosures of which are incorporated herein.
The term "sulfoxidation method" is widely used for the process where sulfur dioxide and oxygen are made to act simultaneously on n-paraffins possibly bearing functional groups or on cycloparaffins to produce paraffin sulfonic acids.
The practically implementable process variables differ first of all by the kind of initiation of the sulfoxidation. Among these known initiation means are ultraviolet light, the ozone method and the gamma-ray process, and processes involving the addition of peroxide compounds. There are furthermore the methods employing acetic acid anhydride, light-water and chlorine as disclosed in CHEMIE IN UNSERER ZEIT, 13, 1979, pp. 157.
As regards the light-water sulfoxidation process, that is, the process where paraffins are reacted with sulfur dioxide, oxygen and water in the presence of ultraviolet light: in addition to the paraffin sulfonic acids desired, also sulfuric acid must be removed in the course of the processing of the sulfoxidation output. The term sulfoxidation output, also within the scope of the present invention, defines the reaction output which is degassed and already freed from most of the unconverted paraffin.
According to the state of the art, the sulfuric acid is removed by treating the sulfoxidation output with an organic solvent in order to induce demixing into an organic phase containing the totality of the paraffin sulfonic acids and into an aqueous phase containing the sulfuric acid as much as possible in the form of a solution which is generally 15 to 25% by weight sulfuric acid. Thereupon the two phases are separated and the organic phase is further processed to isolate the paraffin sulfonic acids or their salts.
This German patent application No. F 3718.120, 32/01 discloses as useful organic solvents benzene, chlorobenzene, cyclohexane, carbon tetrachloride, chloroform, methylene chloride, 1,2-dichloroethane, tetrahydrofuran and the alcohol butanol.
French Pat. No. 14 78 530 discloses the use of quite generally oxygen containing organic compounds such as alcohols, ethers and ketones as organic solvents. Amyl alcohol is especially emphasized from among the groups of alcohols.
As shown by U.S. Pat. No. 4,178,307, which discloses the use of ethers, ketones, esters and (cyclo)-aliphatic ketoesters in columns 2 and 3 as organic solvents, difficulties may arise when alcohols having at least 5 C atoms are used in the continuous process mode as disclosed in U.S. Pat. No. 4,177,208, because following the recovery of the alcohol used it was not sufficiently freed from its sulfonated paraffins.
It is known that aliphatic and cycloaliphatic alcohols having at least 5 C atoms in the molecule can be used as extractants to extract the organic components from a crude sulfonation mixture containing unreacted paraffin, water and sulfuric acid besides the desired sulfonic acids, as disclosed in U.S. Pat. No. 4,177,208. In the process, the sulfuric acid separates in the aqueous phase and thus it can be isolated from the alcohol extract. The unreacted paraffin present together with the sulfonic acids remains in the lighter weight organic phase. The entire amount of paraffin present then is separated after neutralization of the sulfonic acids and removal of the extractant from the sulfonic acids present in the form of alkali sulfonates in a further process stage. This process of U.S. Pat. No. 4,177,208 includes the following steps:
(a) admixing with the paraffin sulfonic acid solution, at least one slightly polar alcohol selected from the group consisting of aliphatic and cycloaliphatic alcohols containing at least 5 carbon atoms, having a solubility in water less than 7% by weight which forms an azeotrope with water, thereby forming a mixture having an organic phase containing paraffin sulfonic acids dissolved therein and an aqueous phase containing the sulfuric acid;
(b) separating the organic phase from the aqueous phase;
(c) neutralizing the separated organic phase by admixture with a composition selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkaline earth metal oxides, alkaline earth metal hydroxides, and alkaline earth metal carbonates thereby converting the sulfonic acids present in the organic phase into sulfonates, and forming a neutralized organic phase wherein the ratio of the amount of water to the amount of slightly polar alcohol in the neutralized phase is at most equal to the corresponding ratio for the azeotrope which forms between water and the slightly polar alcohol; and
(d) removing the volatile components from the neutralized organic phase to recover the sulfonates under temperature and pressure conditions whereby the sulfonates are in a molten state.